[FFmpeg-cvslog] lavu/tx: minor code style improvements and additional comments
Lynne
git at videolan.org
Sat Apr 24 18:19:54 EEST 2021
ffmpeg | branch: master | Lynne <dev at lynne.ee> | Sat Apr 10 03:45:03 2021 +0200| [aa910a7ecd68b41379506998b6a32aa0a2a69dec] | committer: Lynne
lavu/tx: minor code style improvements and additional comments
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=aa910a7ecd68b41379506998b6a32aa0a2a69dec
---
libavutil/tx.c | 17 +++++++++++++++-
libavutil/tx.h | 2 ++
libavutil/tx_priv.h | 57 ++++++++++++++++++++++++++++-------------------------
3 files changed, 48 insertions(+), 28 deletions(-)
diff --git a/libavutil/tx.c b/libavutil/tx.c
index 1161df3285..05d4de30cc 100644
--- a/libavutil/tx.c
+++ b/libavutil/tx.c
@@ -30,7 +30,7 @@ int ff_tx_type_is_mdct(enum AVTXType type)
}
}
-/* Calculates the modular multiplicative inverse, not fast, replace */
+/* Calculates the modular multiplicative inverse */
static av_always_inline int mulinv(int n, int m)
{
n = n % m;
@@ -91,6 +91,17 @@ int ff_tx_gen_compound_mapping(AVTXContext *s)
return 0;
}
+static inline int split_radix_permutation(int i, int m, int inverse)
+{
+ m >>= 1;
+ if (m <= 1)
+ return i & 1;
+ if (!(i & m))
+ return (split_radix_permutation(i, m, inverse) << 1);
+ m >>= 1;
+ return (split_radix_permutation(i, m, inverse) << 2) + 1 - 2*(!(i & m) ^ inverse);
+}
+
int ff_tx_gen_ptwo_revtab(AVTXContext *s, int invert_lookup)
{
const int m = s->m, inv = s->inv;
@@ -117,6 +128,7 @@ int ff_tx_gen_ptwo_inplace_revtab_idx(AVTXContext *s)
if (!(s->inplace_idx = av_malloc(s->m*sizeof(*s->inplace_idx))))
return AVERROR(ENOMEM);
+ /* The first coefficient is always already in-place */
for (int src = 1; src < s->m; src++) {
int dst = s->revtab[src];
int found = 0;
@@ -124,6 +136,9 @@ int ff_tx_gen_ptwo_inplace_revtab_idx(AVTXContext *s)
if (dst <= src)
continue;
+ /* This just checks if a closed loop has been encountered before,
+ * and if so, skips it, since to fully permute a loop we must only
+ * enter it once. */
do {
for (int j = 0; j < nb_inplace_idx; j++) {
if (dst == s->inplace_idx[j]) {
diff --git a/libavutil/tx.h b/libavutil/tx.h
index bfc0c7f2a3..fccded8bc3 100644
--- a/libavutil/tx.h
+++ b/libavutil/tx.h
@@ -49,9 +49,11 @@ enum AVTXType {
* float. Length is the frame size, not the window size (which is 2x frame)
* For forward transforms, the stride specifies the spacing between each
* sample in the output array in bytes. The input must be a flat array.
+ *
* For inverse transforms, the stride specifies the spacing between each
* sample in the input array in bytes. The output will be a flat array.
* Stride must be a non-zero multiple of sizeof(float).
+ *
* NOTE: the inverse transform is half-length, meaning the output will not
* contain redundant data. This is what most codecs work with.
*/
diff --git a/libavutil/tx_priv.h b/libavutil/tx_priv.h
index e2f4314a4f..10d7ea3ade 100644
--- a/libavutil/tx_priv.h
+++ b/libavutil/tx_priv.h
@@ -20,9 +20,7 @@
#define AVUTIL_TX_PRIV_H
#include "tx.h"
-#include <stddef.h>
#include "thread.h"
-#include "mem.h"
#include "mem_internal.h"
#include "avassert.h"
#include "attributes.h"
@@ -48,12 +46,14 @@ typedef void FFTComplex;
#if defined(TX_FLOAT) || defined(TX_DOUBLE)
-#define CMUL(dre, dim, are, aim, bre, bim) do { \
+#define CMUL(dre, dim, are, aim, bre, bim) \
+ do { \
(dre) = (are) * (bre) - (aim) * (bim); \
(dim) = (are) * (bim) + (aim) * (bre); \
} while (0)
-#define SMUL(dre, dim, are, aim, bre, bim) do { \
+#define SMUL(dre, dim, are, aim, bre, bim) \
+ do { \
(dre) = (are) * (bre) - (aim) * (bim); \
(dim) = (are) * (bim) - (aim) * (bre); \
} while (0)
@@ -66,7 +66,8 @@ typedef void FFTComplex;
#elif defined(TX_INT32)
/* Properly rounds the result */
-#define CMUL(dre, dim, are, aim, bre, bim) do { \
+#define CMUL(dre, dim, are, aim, bre, bim) \
+ do { \
int64_t accu; \
(accu) = (int64_t)(bre) * (are); \
(accu) -= (int64_t)(bim) * (aim); \
@@ -76,7 +77,8 @@ typedef void FFTComplex;
(dim) = (int)(((accu) + 0x40000000) >> 31); \
} while (0)
-#define SMUL(dre, dim, are, aim, bre, bim) do { \
+#define SMUL(dre, dim, are, aim, bre, bim) \
+ do { \
int64_t accu; \
(accu) = (int64_t)(bre) * (are); \
(accu) -= (int64_t)(bim) * (aim); \
@@ -93,7 +95,8 @@ typedef void FFTComplex;
#endif
-#define BF(x, y, a, b) do { \
+#define BF(x, y, a, b) \
+ do { \
x = (a) - (b); \
y = (a) + (b); \
} while (0)
@@ -101,7 +104,7 @@ typedef void FFTComplex;
#define CMUL3(c, a, b) \
CMUL((c).re, (c).im, (a).re, (a).im, (b).re, (b).im)
-#define COSTABLE(size) \
+#define COSTABLE(size) \
DECLARE_ALIGNED(32, FFTSample, TX_NAME(ff_cos_##size))[size/2]
/* Used by asm, reorder with care */
@@ -114,35 +117,35 @@ struct AVTXContext {
double scale; /* Scale */
FFTComplex *exptab; /* MDCT exptab */
- FFTComplex *tmp; /* Temporary buffer needed for all compound transforms */
+ FFTComplex *tmp; /* Temporary buffer needed for all compound transforms */
int *pfatab; /* Input/Output mapping for compound transforms */
int *revtab; /* Input mapping for power of two transforms */
int *inplace_idx; /* Required indices to revtab for in-place transforms */
};
-/* Shared functions */
+/* Checks if type is an MDCT */
int ff_tx_type_is_mdct(enum AVTXType type);
+
+/*
+ * Generates the PFA permutation table into AVTXContext->pfatab. The end table
+ * is appended to the start table.
+ */
int ff_tx_gen_compound_mapping(AVTXContext *s);
+
+/*
+ * Generates a standard-ish (slightly modified) Split-Radix revtab into
+ * AVTXContext->revtab
+ */
int ff_tx_gen_ptwo_revtab(AVTXContext *s, int invert_lookup);
+
+/*
+ * Generates an index into AVTXContext->inplace_idx that if followed in the
+ * specific order, allows the revtab to be done in-place. AVTXContext->revtab
+ * must already exist.
+ */
int ff_tx_gen_ptwo_inplace_revtab_idx(AVTXContext *s);
-/* Also used by SIMD init */
-static inline int split_radix_permutation(int i, int n, int inverse)
-{
- int m;
- if (n <= 2)
- return i & 1;
- m = n >> 1;
- if (!(i & m))
- return split_radix_permutation(i, m, inverse)*2;
- m >>= 1;
- if (inverse == !(i & m))
- return split_radix_permutation(i, m, inverse)*4 + 1;
- else
- return split_radix_permutation(i, m, inverse)*4 - 1;
-}
-
-/* Templated functions */
+/* Templated init functions */
int ff_tx_init_mdct_fft_float(AVTXContext *s, av_tx_fn *tx,
enum AVTXType type, int inv, int len,
const void *scale, uint64_t flags);
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